An Interpenetrated Pillar-Layered Metal-Organic Framework with Novel Clusters: Reversible Structural Transformation and Selective Gate-Opening Adsorption

A new metal-organic framework (MOF), [Co-3(tzba)(2)(bpy)(3)(F)(2)]center dot DMF center dot C2H5OH center dot 2H(2)O (1), has been constructed by solvothermal reaction of Co(NO3)(2) with 4-(1H-Tetrazol-5-yl) benzoic acid (H(2)tzba) and 4,4'-bipyridine (bpy) mixed ligands. 1 shows an interpenetrated three-dimensional (3D) pillar-layered framework with the novel trinuclear [Co-3(CN4 )(2)(F-2)] clusters. The pi center dot center dot center dot pi interactions existing among three bpy give rise to an uncommon tripillar in the framework. The framework reveals a reversible dynamic flexibility related to the solvent molecules. Meanwhile, the adsorption of CO2 exhibits an interesting gate opening-closing phenomenon which features the S-shaped isotherms with dramatic hysteretic desorption. The selective adsorption of CO2 over CH4 as well as the adsorption mechanism for CO2 were also discussed deeply.